Polyolefins such as polyethylene (PE) and polypropylene (PP) are light and inexpensive and further have characteristics of having excellent physical properties and workability. On the other hand, high chemical stability of polyolefins is an obstacle for giving, thereto, high functionalities, typical examples of which include printability, paintability, heat resistance and impact resistance, and a function for improving compatibility thereof with other polar polymers. There are known methods for making up for such drawbacks and causing polyolefins to have functionalities. Examples thereof include a method of polymerizing an olefin with a polar monomer such as vinyl acetate or a methacrylic acid ester by radical polymerization; and a method of grafting a polar monomer such as maleic anhydride to a polyolefin in the presence of a peroxide. However, according to these methods, it is generally difficult to control minutely the structure of olefin chain moieties in the resultant polymers. As a result, excellent, original physical properties of polyolefin may be damaged.
In general, it is well known that a process using living polymerization is useful as a process for producing such a polymer. In the case of highly-controlled living polymerization, a growing terminal of the polymer quantitatively keeps reactivity. It is therefore known that the reactivity is used to cause the terminal to react directly with a polar-group-containing monomer, whereby a polymer having a functional group at its terminal position can be effectively produced.
However, in the case of polymerizing any olefin by living polymerization, chain transfer reaction of the growing polymer chain is frequently caused under ordinary conditions; therefore, it is very difficult to produce an olefin polymer by living polymerization. Some examples wherein an α-olefin is subjected to living polymerization have been reported so far. However, in any one of the report examples, the polymerization is conducted at a very low temperature in order to control chain transfer reaction. The polymerization activity thereof is also a low value. The molecular weight thereof is also at most several tens of thousands. Furthermore, monomers that can be polymerized are restricted in many cases. It is particularly difficult to produce industrially important ethylene-based (co) polymers or block copolymers. Concerning stereoregular polymerizations of α-olefins, living polymerizations exhibiting a high regularity are hardly known (see, for example, “Kobunshi”, 1988, 47(2), 74-77).
Under such situations, the Applicant already discloses a transition metal compound having a salicylaldimine ligand as a novel catalyst for olefin polymerization (see Japanese Patent Application Laid-Open No. 11-315109), and further suggests a process of using the transition metal compound to produce a novel single-terminal vinyl-group-containing copolymer or a novel polar-group-containing block copolymer (see Japanese Patent Application Laid-Open Nos. 2003-73412 and 2003-40953). However, the two published documents neither disclose any polymer having a polar functional group only at its single terminal (single-chain-end functionalized polymer) nor any process for the production thereof. The present Applicant has eagerly searched a single-chain-end functionalized polymer which can be used for various purposes and has overcome the above-mentioned problems, and has then made the present invention.